1. Field of the Invention
The invention relates generally to inspection instruments, and more particularly to a system and device for detecting and characterizing tissue and a method thereof.
2. Description of Related Art
Certain types of vulnerable plaques in a patient's vasculature are likely to rupture. These plaques, once ruptured, are extremely dangerous and can swiftly cause the patient's death. It is therefore desirable to detect the existence of such high-risk plaques so that they can be disposed of before they rupture.
High-risk plaques are believed to be characterized by large lipid pools hidden behind vascular walls. Because these lipid pools are covered by vascular walls, they cannot be seen by visible light. However, infrared light can penetrate short distances into the vascular wall and can therefore be used to detect such plaques, as well as other intravascular pathology.
A difficulty associated with intravascular use of infrared radiation is that blood absorbs and scatters such radiation. This results in a reduction in the signal-to-noise ratio. As a result, it is desirable to minimize the extent to which infrared radiation propagates through the blood.
Various techniques, however, exist or are being developed to detect plaque or lesions and malformations using probes inserted by, for example, a catheter and placed in proximity to anatomical features that are or might cause health problems. Examples include Low-Coherence Interferometry (LCI) for sensing tissue characteristics or its related imaging embodiment, Optical Coherence Tomography (OCT).
LCI is an optical technique that relies on “coherence gating” to provide precise axial positioning of an object in the direction of light propagation. By focusing the light in a sample, a transverse resolution may also be obtained (perpendicular to the optical beam), thus allowing for the collection of information from a finite volume for imaging or optical characterization purposes.
OCT is an imaging technique which allows high resolution observation and characterization of tissue microstructure imaging with resolution on the order of microns. This technique measures detailed changes within a few millimeters of a non-transparent tissue structure. One drawback of OCT imaging is the time to acquire a large number of data points necessary to obtain an image over a sufficient area.
An example of removing blood from a measurement site is to purge or flush the site with saline solution. This technique provides a short window of opportunity during which a measurement can be taken through the transparent saline solution. However, once the saline disperses, blood flows back into the measurement site and obscures the vascular wall.
Another approach to removing blood from a measurement site is to displace it with an inflated balloon catheter. However, if the balloon is not sufficiently inflated, considerable blood remains between the balloon and the vascular wall. If the balloon is so inflated that it makes contact with the vascular wall, blood flow is obstructed. This can lead to ischemia at points downstream from the balloon. In addition, the pressure of the balloon on the vascular wall can trigger a rupture of the plaque.
Accordingly there is a need for a device and method for sensing or characterizing arterial tissue and minimizing light attenuation in blood to improve a signal-to-noise ratio to achieve better results.